line in a JLabel that disappear when adding to a new frame

import java.awt.*;

import java.awt.event.*;

import javax.swing.*;

public class SF extends JFrame {

private JPanel jPanel1;

public SF() {

// Initialize components.

jPanel1 = new JPanel(new CardLayout());

jPanel1.add(new SP(10,10,100,100,Color.red), "sample 1");

jPanel1.add(new SP(50,150,200,50,Color.blue), "sample 2");

JButton jButton1 = new JButton("OK");

jButton1.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent evt) {

CardLayout cl = (CardLayout)(jPanel1.getLayout());

cl.next(jPanel1);

}

});

JPanel south = new JPanel();

south.add(jButton1);

// Configuration and assemble JFrame.

setDefaultCloseOperation(EXIT_ON_CLOSE);

add(jPanel1);// Default center section.

add(south, "Last");

pack();

setLocation(200,200);

setVisible(true);

}

public static void main(String[] args) {

new SF();

}

}

class SP extends JPanel {

private int x1;

private int y1;

private int x2;

private int y2;

private Color color;

public SP(int x1, int y1, int x2, int y2, Color c) {

this.x1 = x1;

this.y1 = y1;

this.x2 = x2;

this.y2 = y2;

color = c;

}

protected void paintComponent(Graphics g) {

super.paintComponent(g);

g.setColor(color);

g.drawLine(x1, y1, x2, y2);

}

// You may need this if you are going to call pack

// on the top-level container of this component.

// Return whatever dimensions you want this to be

// displayed with by the parent. Those that respect

// preferredSize will honor it. Otherwise, it may be

// shown at its default size of (10, 10) or even (0, 0).

public Dimension getPreferredSize() {

return new Dimension(300, 200);

}

}

crwooda at 2007-7-7 23:58:43 >

Try changing your implementation of SP to this:

class SP extends JPanel {

private int x1;

private int y1;

private int x2;

private int y2;

private Color color;

public SP(int x1, int y1, int x2, int y2, Color c) {

this.x1 = x1;

this.y1 = y1;

this.x2 = x2;

this.y2 = y2;

color = c;

setLayout(new BorderLayout());

add(new DrawingLabel());

}

private class DrawingLabel extends JLabel {

protected void paintComponent(Graphics g) {

g.setColor(color);

g.drawLine(x1, y1, x2, y2);

}

}

public Dimension getPreferredSize() {

return new Dimension(300, 200);

}

}

crwooda at 2007-7-7 23:58:43 >

The changes you posted last work okay (j2se 1.5). The JLabel is non–opaque and allows the

colored lines on the panel surface to show through. The question is why do you want to

draw on the JPanel and place a JLabel on top of the drawing? Usually when we do graphics

we do all the drawing on a JPanel and do not add any components (except maybe a Border) to

it. Then use the JPanel as a component with other components. Adding components to a

JPanel with graphics on it covers up the graphics. Can you say what you are trying to do?

Maybe there is an easier/more productive/less tricky way.

If you must add a JLabel with graphics you could try to place it in say the north or south

sections of a BorderLayout or use a GridBagLayout. It is usually easier to draw the text

in with the graphics and avoid problems with other components, layout managers, resizing

behavior, etc.

crwooda at 2007-7-7 23:58:43 >

the app need to receive a pain event to show the line..

You can have a boolean in SP (member variable) that can control whether or not something

is drawn in paintComponent. This boolean value can be changed by another class in

your app, for example, with user input through a JCheckBox.

reuse an old frame (oldFrame) which has some drawings, these drawings are on several

labels of the oldFrame

I'm confused.

crwooda at 2007-7-7 23:58:43 >

Hi again crwood!!

Okay, you're taking the content pane, a Container, from a top杔evel container (you mentioned a frame, "oldFrame"). And this container contains some JLabels which have lines drawn in them. You want to add this container to a card in a Cardlayout. Okay, so far so good.

That磗 exactly what I want ;).

So (using your code):

I have the panel:

class SP extends JPanel {

private int x1;

private int y1;

private int x2;

private int y2;

private Color color;

private JLabel label;

public SP(int x1, int y1, int x2, int y2, Color c) {

this.x1 = x1;

this.y1 = y1;

this.x2 = x2;

this.y2 = y2;

color = c;

setLayout(new BorderLayout());

label =new JLabel();

add(label);

}

protected void paintComponent(Graphics g) {

super.paintComponent(g);

label.getGraphics().setColor(color);

label.getGraphics().drawLine(x1, y1, x2, y2);

}

public Dimension getPreferredSize() {

return new Dimension(300, 200);

}

}

And the main frame:

public class SF extends JFrame {

private JPanel jPanel1;

public SF() {

// Initialize components.

jPanel1 = new JPanel(new CardLayout());

jPanel1.add(new SP(10,10,100,100,Color.red), "sample 1");

jPanel1.add(new SP(50,150,200,50,Color.blue), "sample 2");

JButton jButton1 = new JButton("OK");

jButton1.addActionListener(new ActionListener() {

public void actionPerformed(ActionEvent evt) {

CardLayout cl = (CardLayout)(jPanel1.getLayout());

cl.next(jPanel1);

}

});

JPanel south = new JPanel();

south.add(jButton1);

// Configuration and assemble JFrame.

setDefaultCloseOperation(EXIT_ON_CLOSE);

add(jPanel1);// Default center section.

add(south, "Last");

pack();

setLocation(200,200);

setVisible(true);

}

public static void main(String[] args) {

new SF();

}

}

The problem is I cant see the black line...

(I am able to see it by moving the window until hide part of it)

naskara at 2007-7-7 23:58:43 >

This is a very strange thing... Have you tried the code where the lines are painted on the label?

I am still getting the same results...

Thats what I can see when I execute the app:

http://img507.imageshack.us/my.php?image=snap1dk3.png

And this when I hide part of the window:

http://img505.imageshack.us/my.php?image=snap2qe1.png

naskara at 2007-7-7 23:58:43 >